RFR: 8304138: [JVMCI] Test FailedSpeculation existence before appending. [v2]

Tue Mar 14 16:00:31 UTC 2023

On Tue, 14 Mar 2023 15:34:50 GMT, Yudi Zheng <yzheng at openjdk.org> wrote:

>> Upon uncommon_trap, JVMCI runtime appends a FailedSpeculation entry to the nmethod using an [atomic operation](https://github.com/openjdk/jdk/blob/55aa122462c34d8f4cafa58f4d1f2d900449c83e/src/hotspot/share/oops/methodData.cpp#L852). It becomes a performance bottleneck when there is a large amount of (virtual) threads deoptimizing in the nmethod. In this PR, we test if a FailedSpeculation exists in the list before appending it.
>
> Yudi Zheng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   avoid iterating from beginning.

Marked as reviewed by dnsimon (Committer).

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PR: https://git.openjdk.org/jdk/pull/13022